Routers are used to remove material from a workpiece for decorative or functional purposes. In particular, routers may be useful in performing cabinetwork, cutting grooves in the surface or edges of a material, and applying a decorative border to a material through fluting or beading. In general, there are two types of routers, namely fixed base routers and plunge base routers. Both types of routers include an electric motor having a rotating shaft mounted vertically within a housing. The motor shaft terminates with a chuck, clamp, or collet for interchangeably securing a cutting tool, referred to as a router bit, to the shaft for rotation with the shaft. Fixed base routers and plunge base routers exhibit structural differences that affect the method by which the routers are operated.
Fixed base routers include a motor unit coupled to a base having a motor mount, two opposing handles, and a work engaging surface. The motor mount is connected to the top of the work engaging surface. The handles are connected to the motor mount and/or the top surface of the work engaging surface. A router bit, coupled to the motor unit, is configured to extend through an opening in the work engaging surface. The amount the router bit extends from the work engaging surface is adjustable depending on the position of the motor unit relative to the motor mount. In particular, the motor mount may include a plurality of different positions in which the motor unit may be locked. The plurality of positions enables a user to make grooves or cuts of a particular depth, depending on which position is selected. In general, a user operates a fixed base router by precisely guiding the rotating router bit around the edges or surface of a workpiece, thereby causing the bit to cut and remove portions of the workpiece at a fixed and predetermined depth.
Plunge base routers include a carriage, two opposing handles, a base plate, and two plunge posts. The plunge posts extend perpendicularly from the base plate and extend into channels formed in the carriage. The carriage is configured to house an electric motor, wherein the rotating shaft of the electric motor extends downward from the carriage toward the base plate. The opposing handles are connected to opposite sides of the carriage. Biasing members are configured to bias the carriage in an upward direction away from the base plate so that the motor shaft and the router bit, if one is attached, are positioned above the base plate, out of contact with a workpiece. A user may apply downward pressure upon the opposing handles, to slide the carriage down the plunge posts toward the workpiece until the router bit extends below the base plate by a predetermined distance. Thus, the term “plunge” refers to the ability of a plunge base router to direct a router bit into contact with a workpiece from the upper position in which the router maintains the rotating router bit above the workpiece, to the lower position in which the router bit is forced into contact with the workpiece. Upon releasing the downward pressure on the handles, the biasing system forces the carriage to slide up the plunge posts to the upper position, thereby removing the router bit from contact with the workpiece.
Plunge base routers may be configured to include guide bearings to enable the carriage to slide smoothly upon the plunge posts. Known plunge base routers utilize roller bearings seated within channels in the carriage to guide the carriage upon the plunge posts. Roller bearings deliver acceptable results; however, routers utilizing rollers bearings are expensive to manufacture due to the low tolerance levels required for smooth operation of the bearings. For instance, if the separation between the plunge posts does not align precisely with the separation of the bearings, the plunge posts may bind against the bearings resulting in a router that does not smoothly slide upon the plunge posts. Other plunge routers utilize o-rings to stabilize and guide the plunge posts within the carriage; however, o-rings require a source of lubrication which may be undesirable for some users. Thus, a router having an improved plunge post bearing system is desirable.